Refrigerator unit used for a freight container

ABSTRACT

A refrigerator unit used for a freight container which may be operated at various places where the line voltages of available power are different, for example, 200 v. class and 400 v. class, said unit comprising electric loads rated for the dual voltages, switches for selecting appropriate power input terminals or relays for detecting the voltage of the connected power line, switches for changing connections of the electric loads so as to match the rated voltage of said loads with the power voltage, the above switches and relays being all interconnected to ensure safe operation.

United States Patent 1 1 3,601,618

[72] Inventors Toshiyuki'loyonaka [50] Field of Search 31 307/10, ll,Yokohama; l8, I9, 43, I7, 64, 75, 80; 318/225, 226 Akira Goto,Sakai-ski; Joji Ochi, Osaka; Katsumasa Hatamoto, Sakai-shi; Tetsuji lReferences Cited Arai, Funabashi-shi, all of, Japan UNITED STATESPATENTS P 841336 2,693,539 11/1954 Madigan 307/10 [22] Filed July 14,1969 [45] Patented Aug. 24, 197] Primary Examiner-Robert K. Schaefer[73] Assigns: Daikin Kogyo Co. u Assistant ExaminerH. J. Hohauser Osaka,Japan Attorney-Cushman, Darby & Cushman [32] Priority July 20, 1968,Jan. 30, 1969,,Ian. 17, 1969 {33] Japan [3]] 43/62233, 44/8039 and44/4134 AB STRACT: A refrigerator unit used for a fre1ght containerwhich may be operated at vanous places where the line voltages ofavailable power are different, for example, 200 v. class and 400 v.class, said unit comprising electric loads rated for [54] gg gggfi aUNIT USED FOR A FREIGHT the dual voltages, switches for selectingappropriate power 13 Claims u Drawing g input terminals or relays fordetecting the voltage of the connected power line, switches for changingconnections of the [52] US. Cl 307/9, electric loads so as to match therated voltage of said loads 3 18/225 with the power voltage, the aboveswitches and relays being all [5 l 1 Int. Cl "02g 3/00 interconnected toensure safe operation.

PATENTED M1824 ran sum 1 or 6 PATENTED Auczmn SHEET 3 [IF 6 PATENTEUM1824 IQTI SHEET [1F 6 REFRIGERATOR UNIT USED FOR A FREIGHT CONTAINERThis invention relates to a refrigerator unit used for a freightcontainer, particularly to the electric system of such a refrigeratorunit which is adapted for use in places of different line voltage.

A freight container, in this specification, means an enclosed andthermally insulated box equipped, or adapted to be equipped, with arefrigerator including for example a compressor, condenser, expansionvalve and a cooler as well as electric motors and heaters, which is usedfor transporting perishable goods, being carried on board a lorry orship.

Such a container, as is natural from its object of use, is oftentransported to various countries of the world by land as well as by sea,or periodically transferred between two places. Unfortunately, however,the line voltage of power distribution systems are not the samethroughout the world. It differs with countries, areas within a country,ships, railroads and even between firms. The line voltages are generallydivided into two categories, 200 v. class and 400 v. class. On the otherhand, conventional refrigerated containers are generally rated for asingle class of voltage. This has been hindering refrigerated containersfrom being conveniently used in a larger sphere. In certain cases, ithas been necessary to install a special power unit to accommodaterefrigerated containers.

The main object of this invention is to provide a refrigerator unit fora freight container which can be easily and safely operated with eitherof the line voltages of the above-mew tioned two voltage classes.

In order to achieve the above object, the refrigerator unit of thisinvention comprises electric motors constructed so as to be adaptable toeither of the two classes of line voltages by simply changing theelectric connections of said motor, a first means which contributes todiscriminate said two classes of line voltages, a second means forchanging said electric conncctions of said motors, and a third means forinterlocking said first means with said second means so as to match therated voltage of said motors with the voltage of the power line withwhich said refrigerator unit is connected.

More specifically, in one aspect of this invention, the refrigeratorunit includes dual-rated electric motors and heaters, and switches forselecting connections of said electric apparatuses, power supplycircuits and control circuits according to the class of line voltage,said switches being mutually interlocked so that no danger will occureven if a wrong power switch is turned on or the power cable has beencon nected with a wrong power outlet, and moreover the refrigerator unitis provided with two power connectors of different types, each to beconnected with the respective power source of the different voltageclasses, in order to minimize the probability of misconnection.

In another modification of this invention, the above-mentioned switchesare further interlocked with electromagnetic contactors through whichthe loads are controlled, to prevent the switches from dealing withheavy current at the start and stop of the motors.

In still another modification of this invention, the refrigerator unitis provided with a transformer which is inserted into the power line orbypassed by means of a switch depending on the class of the linevoltage, so that the unit can be operated with either of the linevoltages.

In a further modified type of this invention, the refrigerator unitincludes an automatic switching device in the control circuit, whichdetects the class of the line voltage and makes appropriate connectionsof the electric apparatuses or loads according to the voltage class, itbeing only necessary for the operator to connect the unit with the powersource.

In a still further modification of this invention, the refrigerator unitincludes current detecting elements for protecting a motor fromoverload, which are connected in a manner that the same detectingelements are equally effective for an operation under either of twoclasses of line voltage.

Other objects and features of this invention will be clarified in thefollowing description given in connection with embodiments of theinvention and with reference to the accompanying drawings, in which;

FIG. I is a connection diagram of an embodiment of this invention inwhich the switching of the electric connections are performed withmanual switches;

FIG. 2 is a connection diagram of an embodiment of a simpler type of therefrigerator unit of this invention, of which the manual switches can beintegrated into a compact cam switch;

FIG. 3 is a diagram showing the operational sequence ofthe cam switchwhich may be used in the embodiment shown in FIG. 2',

FIG. 4 is a connection diagram of an automatic type of embodiment ofthis invention;

FIG. 5 is a connection diagram of another automatic type of embodimentof this invention;

FIG. 6 is a block diagram of the static voltage relay which is used inthe embodiment shown in FIG. 5;

FIGS. 7a and 7b are connection diagrams of windings in a dual-ratedthree-phase induction motor used in this invention, FIG. 7a being foruse with a 400 v. class line voltage and FIG. 7b for use with a 200 v.class voltage;

FIGS. 8a and 8b are connection diagrams of windings in a dual-ratedsingle-phase induction motor used in this invention, FIG. 8a being forthe use in a 400 v. system and FIG. 8b for the use in 200 v. system; and

FIG. 9 is a connection diagram of an embodiment of this invention inwhich a transformer is used for adapting the loads to the line voltageof the different voltage classes.

In the above drawings, it should be noted that the motors shown in FIGS.1, 2, 4 and 5 have been assumed to have the connections as shown inFIGS. 7a and 7b, and that singlephase motors and heaters are not shownin FIGS. 4 and 5 just for simplification of the explanation. Also, inFIG. 2, heaters are omitted for the same reason.

Throughout the drawings, the whole connection diagram of therefrigerator unit is divided into three sections, that is, inputsection, load section and control section, respectively being indicatedby characters A, B and C. Generally, characters R, S, T indicate powerinput terminals; particularly R,, S,, T, being such terminals which areto be connected with 200 v. class power lines, while R 8,, T are for 400v. class power lines.

Referring to FIG. I, P, and P indicate plugs connected with the inputterminals R,, S,, T, and R 8,, T respectively through appropriatecables. Plugs P, and I have respectively different formations so as notto allow misconnection. That is to say, plug P, is adapted only to a 200v. receptacle, while plug P only to a 400 v. receptacle. Referencecharacter CB indicate a circuit breaker. The refrigerator includes acompressor, a condenser, an expansion valve and a cooler whichconstitute the known refrigerating cycle. In other words, the electricload includes a compressor motor M,, fan motors M and M for thecondenser, and fan motors M and M for the cooler. The compressor motorM, is a dual-voltage threephase induction motor and has delta-connectedstator windings. Each branch of the delta consists of two windings whichare to be connected in series for use in 400 v. lines as shown in FIG.7a or connected in parallel for use in 200 v. lines as shown in FIG. 7b.The fan motors M M M, and M are single-phase induction motors. For 400v. operation, windings of the single-phase motor may be connected asshown in FIG. 8a. That is, the main coil (u,v,) is connected in parallelwith the series connection of the auxiliary coil (u, y) and a capacitor,and an additional coil (u -v is connected in series with the aboveparallel connection. FOr 200 v. operation, the connection should be asshown in FIG. 8b, the additional coil also being connected in parallelwith the abovementioned parallel connection. Electromagnetic contactorsMS, controls the compressor motor M, and the condenser motors M and Mwhile electromagnetic contactor MS controls the fan motors M and M, ofthe cooler. Reference character WS indicates a water switch. Therefrigerator unit further includes a heater h, for defrosting thecooling coils and heating air, a second heater h for a drain pan and athird heater h, for a drain tube. These heaters h I1 h also are preparedfor connection to either of 200 v. and 400 v. lines. An electromagncticcontactor MS, controls the heater load.

Reference character SS indicates a gang switch such as a multistage camswitch or a rotary switch, which is manually operated. The switchtraversed by a dotand-dash line in the Figure are all included in thisgang switch SS, of which switch contacts indicated with H are ones to beclosed in the 400 v. operation, whereas those marked with L are closedin the 200 v. operation, interlock means being provided lest a H contactand a L contact should be closed at the same time. A transformer Tr isprovided for supplying a control circuit with elec tric power. Thesecondary winding of the transformer Tr is provided with a midtap. Inoperation with a 200 v. source, the switch contact L is closed toconnect one of the output terminals T and S of the transformer with oneend of the secondary winding; while in the operation with a 400 v.source, the midtap is connected with said one of the output terminalsthrough the switch contact H. Thus, under either line voltage, the samevoltage 24 v. appears across the output terminals T and S to which isconnected the control circuit of the electromagnetic contactors.

Operation of the above-described control system will be explainedhereunder. Assuming that a 400 v. power line is now available, the inputterminals R S T are connected with the power line or the input plug P isinserted to a mating power receptacle after the gang switch SS is turnedso as to close the H contacts, and then the circuit breaker CB isclosed, which is followed by closing the electromagnetic contactors M5,,M8 MS through adequate control means (not shown). Thus, a 400 v. poweris applied to the loads which have all been prepared for operation under400 v. In this case, if it happens that the gang switch SS is mistakenlyturned to make the L contacts, thereby changing the connections in theloads to a 200 v. rating, none of the electric apparatuses will bedamaged, since the 400 v. input also is cut off by the gang switch SSitself (H contacts in A section).

Next, assuming that a 200 v. power is available, the input terminals R,,S,, T, or the input plug P, is connected with the power line, after thegang switch SS is turned so as to close the L contacts. Then the circuitbreaker CB and the electromagnetic contactors M8,, M5 M8 are closed inthe same manner as in the previous case. Thus, the operation will start,200 v. power being applied to the load adapted for the same voltage. Ifthe gang switch SS is mistakenly operated to make the H contacts, nodamage will occur as the power input is also cut off by the same gangswitch SS.

Furl! er, by using the power plugs P, and P which have electrodes ofdifferent formations from each other and mate only with the properreceptacles, any damage or fault due to a misconnection of the power ora misoperation of the switches is absolutely eliminated.

Now, another embodiment of this invention will be described hereunderwith reference to FIGS. 2 and 3. The control system shown in FIG. 2 issubstantially the same as that shown in FIG. I, except that some of thesingle-phase motors and the heaters are omitted in FIG. 2 in order tosimplify the description of the operation of the gang switch inconnection with FIG. 3. A transformer Tr, for supplying electric powerto the control circuits of the electromagnetic contactors MS,, MS, isprovided with a midtap in the primary wind ing. In 400 v. operation, thepower lines should be connected across both ends of the primary winding;while in 200 v. operation the power lines should be connected to themidtap and one end of the primary winding, so that a constant 24 v.secondary voltage is always maintained between the terminals R and S Itwill be understood that this dual voltage arrangement can be made in thesecondary side of the transformer as in the first embodiment.

The switch contacts L,-L and H,-H., are incorporated into a single camswitch. The arrangement of the contacts are shown in FIG. 3. In FIGS. 2and 3, L, and H, indicate contacts for selecting the power input betweena 200 v. line and a 400 v. line; L L and H contacts for changingconnection of the windings of the compressor motor M,-, L,, L, and H,for changing connection of the windings of a single-phase motor M and Land H, for selecting the primary terminal of the transformer Tr,.

In the case where 200 v. power is available, the cam switch SS is turnedto the position of notch No. I after the power plug P, is fitted to amating power outlet. Thus, the contacts L,L are closed and H,-H., areopened, thereby supplying 200 v. power to the loads that are adapted forthe same voltage. When the available power is 400 v. the cam switch SSis turned to notch No. 4 after the plug P is fitted to a 400 v. poweroutlet. This time the contacts H,--H are closed and L,L are opened, andthe 400 v. power is supplied to the motors M,, M and the transformer Tr,which are all adapted to receive 400 v. power. The cam switch SS isprovided with locking indents at the positions of notches No. I and No.4, but such a locking means is not provided at the other positions, No.2, No. 3 and the neutral point 0. The contacts of the switch SS aredisposed in such a manner that in turning the switch SS by means of alever from the notch No. 1 to notch No. 4 through notches No. 2, 0, No.3, the contact L is opened immediately after the switch lever departsfrom the notch No. 1, while the other L contacts are opened only afterthe leer passes the notch No. 2. Further, the contacts H,I-I are closedat the position of the notch No. 3, but thecontact H, is closed onlyafter the lever reaches the notch No. 4. In a reverse operation,similarly, only the contact H is opened when the lever leaves the notchNo. 4 and the other contacts H,-H are opened after the notch No. 3 ispassed. Further, the contacts L,L are closed at the notch No. 2, whereasthe contact L is closed only after the lever reaches the notch No. I. Itshould be noted that the switch SS is constructed in a manner that thelever cannot be turned from the notch No. 1 directly to No. 4 notpassing the notches No. 2, 0, No. 3, and vice ver- By theabove'described structure of the cam switch SS is ensured safety in theoperation relating to the selection of power voltage. Further, thecurrent interrupting capacity of the contacts in the cam switch can begreatly reduced, which results in such a switch of being constructed amuch smaller size and having a longer life. That is, if the lever of thecam switch happens to be turned during operation of the refrigeratorunit, the contact H (or L is opened prior to opening of the othercontacts H,-H (or L,-L and therefore the electromagnetic contactors MS,,MS, which are designed to properly handle the respective load currentsand which are energized from the transformer Tr, are opened prior toopening of the contacts H,-H (or L,-L Moreover, in starting therefrigerator unit, the contacts H,H (or L,L,-,) will always be closedprior to closing of the electromagnetic contactors. Thus, the contactsof the cam switch SS are assuredly exempted from dealing with heavycurrents during the starting and the stopping periods of the operation.It should be noted, however, that it is usual practice in starting therefrigerator unit to energize the electromagnetic contactors MS,, MSmanually by a pushbutton or automatically after the cam switch SS is setat the notch No. I or No. 4. Further, it should be understood that thecam switch SS may be remotely operated by means of a pilot motorincorporated therein. Other merits with this embodiment are the same asthose described in connection with the previous embodiment.

Still another embodiment of this invention will be described withreference to FIG. 4. In this third embodiment, the switching of theconnections is achieved automatically using electromagnetic contactorswhich are mutually interlocked in the operation. A transformer Tr whichsupplies control power is provided a center tap 12 in the secondarywinding. The transforming ratio of the transformer is such that if 400v. is applied to the primary winding, 48 v. appears between both end b,and c of the secondary winding, while 24 v. appears between the end andthe center terminal b Between terminals b and c is connected aquick-acting auxiliary relay MR, which is rated for 24 v. Anotherauxiliary relay MR of slow-acting type is connected between theterminals b, and c The latter relay MR also is rated for 24 v., but itcan be operated at 48 v. for a short time. Switch contacts indicated byMS are make-contacts of an electromagnetic contactor whose coil isindicated by MC and switch contacts marked with M8, are actuated by coilMC On the other hand, contacts M8,, and MS, are break-contacts, i.e.,normally closed contacts respectively associated with coils MC and MC,Further, contacts mr, and mr are normally open contacts of the relaysMR, and MR respectively, and contacts mr, and mr, are normally-closedcontacts of the relays.

Operation of this embodiment will be described hereunder. Assuming thatthe input terminal R. S, T are connected with three-phase 400 v. powerlines and that circuit breaker CB is closed, voltage of 400 v. isapplied to the transformer Tr and a voltage of 48 v. appears betweenterminals b, and 0 while 24 v. appears between b and 0. Accordingly, 24v. is applied to the relay MR, and 48 v. to the relay MR Though bothrelays start to operate at the same time, the relay MR, acts faster thanthe other. It should be restated here that the relay MR, is of aquick-acting type whereas the relay MR is a slow-acting relay.Therefore, a normally-closed contact mr, of the relay MR, cut off thepower to the relay MR before the latter can make any significant move.Thus, only the relay MR, is actuated, while the relay MR remainsunenergized. Accordingly, the coil MC of the electromagnetic contactoris energized through two normally-open contacts mr, and twonormallyclosed contacts mr to close contacts MS and to open the contactM8,, connected in series with coil MC Meanwhile, the inactivity of theelectromagnetic contactor MC, is ensured by two normally-closed contactsmr, of the relay MR, and a normally-closed contact MS,, of the contactorMC and therefore the contacts MS remain open. Thus, the compressor motorM, is prepared for operation under 400 v., and upon closingelectromagnetic contactor MS,, the motor M, will start safely.

If the line voltage is 200 v., that voltage is applied to thetransformer Tr upon closing the circuit breaker CB. In the secondaryside of the transformer, 24 v. and 12 v. will appear between terminalsb, and c, and between terminals b and 0, respectively. Therefore, 12 v.is applied to the relay MR, and 24 v. to the relay MR As the relay MR,is designed to operate under 24 v. optimum voltage, it will not operatednow with a voltage as low as l2 v. Thus, only the relay MR is actuated,and the coil MC, of the contactor is energized to close the contacts MSwhile the coil MC is prevented from being energized, thereby to keep thecontacts MS opened, in a similar manner as previously described.Therefore, the motor M, is adapted for 200 v. operation and will startsafely upon closing the contactor M8,.

As described above, an automatic switching of the connections in theload according to the class of line voltage is made possible byutilizing a combination of two relays which have difierent operatingcharacteristics.

In the above embodiment, two relays have been used for detecting linevoltages. These relays can be replaced with a semiconductor static relaywhich will be described hereunder referring to FIGS. and 6. In FIG. 5,reference character Tr indicates a stepdown transformer, Ry a voltagerelay of a static type and MR,, an auxiliary relay with contacts Ta, Tb,Tc. The components of substantially the same functions as those shown inFIG. 4 are indicated by corresponding reference characters.

Assuming that the input terminals R, S, T are connected with 400 v.power lines and the circuit breaker CB is closed, that voltage isapplied to the transformer Tr, and a predetermined appropriate voltageappears between two secondary terminals. The static relay Ry comprises,for example, a rectifying and filtering circuit, a voltage detectingcircuit, a voltage regulating circuit and a driving circuit, as shown inFIG. 6. Es-

sential components of the above circuits are semiconductor elements suchas silicon rectifiers, transistors and SCR. Output of the transformer Tris converted to a DC voltage through the rectifier and filter 61, andthe DC-converted voltage is compared with a reference voltage form thevoltage regulator 62, in the voltage detector 63. The resultant signalof the comparison indicating which voltage is higher, is applied to thepower circuit 64, which in turn produces a constant output or no outputdepending on the level of the input voltage.

The circuits of the relay are set so that said output is produced if theline voltage is in the 400 v. class but not ifit is in the 200 V. class.The output from the static relay Ry energizes the auxiliary relay MR toswitch its movable contact T, from the normally-closed position (T tononnally-opened position (T Accordingly, the coil MC is energized toclose the contacts MS and the coil MC, remains inactive to keep thecontacts MS, opened. Thus, the motor M, is prepared for 400 v.operation, and if a pushbutton (not shown) is depressed to close thecontactor MS,, it will start safely.

If the line voltage is 200 v., no output will be produced from thestatic relay Ry as mentioned above. Therefore, the movable contact T ofthe auxiliary relay MR remains at the normally-closed position (T,,) andthe coil MC, of the contactor is energized to close the contacts Ms,,.While, the contacts MS are kept open. The other operations of the systemis the same as those in the preceding embodiment.

In the above embodiments, it will have been noted that overloaddetecting elements 0C are connected among windings of the compressormotor M, in a particular manner. The conventional arrangement ofoverload detecting elements for a motor that is adaptable to two classesof line voltages, has been to connect two sets of such elements ofdifferent current ratings, each set for each line voltage, in serieswith a motor switch or breaker in two of the power lines or in all ofthree lines. With such an arrangement, however, the manufacturing costinvolved in said elements as well as the space in the control boxrequired for them are duplicated. Further, means for selecting eitherset of said two sets of elements according to the line voltage isrequired.-

The above disadvantages have been overcome by the present invention.With the arrangement of this invention, a single set of overloaddetecting elements is equally effective to protect the motor in eitheroperation under 200 v. or 400 v. Such overload detecting elements per seare known art such as various types of combinations of heating elementsand temperature-sensitive bimetallic element or electromagnetic coilswith plungers; and it will be needless to explain that such a detectingelement, if an overload occurs, triggers a nonnallyclosed contact in acontrol circuit of the electromagnetic contactor thereby to open thecontactor and to stop the motor.

In FIGS. 7a and 7b, reference characters R, S, T indicate power inputterminals; U,, U,, V,, V W,, W X,, Y,, Z, terminals of the componentwindings of the motor M, shown in FIGS. 1, 2, 4 and 5; and d, e,f, d,,e,,f,, d e ,f conductors between windings. In the 400 v. operation ofthe motor M,, as shown in FIG. 7a, the overload detecting elements areconnected in the portions d, e, f, or in either two of said threeportions, in order to detect an overload current in the windings if itoccurs. On the other hand, in a 200 v. operation when the windings areconnected as shown in FIG. 7b, the same detecting elements with the samecurrent rating are inserted in the portions d, (or d e, (or e ),f, (orfor either two of said three portions, to protect the motor from theoverload. COmparing the above two cases of the operation, the linecurrents to the motor are of course different, the current in the 200 v.operation being approximately twice as large as for the 400 v.operation. However, the current flowing through each of the sixcomponent windings are the same in both cases, because in a 200 v.operation the phase current (i.e. the current between lines) which istwo-fold that of the 400 v. operation is divided between two componentwindings as is obvious from FIGS. 7a and 7b. Thus, the overloaddetecting elements of the same characteristics can be used with equaleffectiveness in both cases, if they are connected with the windings ina manner as described above. The above explanation has been given withregard to a delta-connected motor. However, it will be obvious that thesame is applicable also to a star (Y)-connected motor.

Further, it will be noted that if the ratio of two anticipated linevoltages is nearly \B, for example, if the power voltage available onboard ship is 200 v., while it is 350 v. at the country of destination,a three-phase motor can be satisfactorily operated at both places simplyby changing the connection of the component windings from a deltaconnection to a star (Y) connection. In such a case, if the overloaddetecting means are connected in series with the component windings asdescribed in the preceding paragraphs, said detecting means will beequally effective in protecting the motor both in 200 v. and 400 v.operations, because the normal current flowing through each componentwinding is the same in both cases, though the line currents aredifferent.

Thus, the above-described arrangement of the overload detecting means inthe three-phase motor adds notable merit to the invention when used inassociation with the switching systems described in the aboveparagraphs.

Finally, still another embodiment of this invention will be describedhereunder with reference to FIG. 9. The control system shown in FIG. 9includes a stepdown transformer Tr besides a small transformer Tr forcontrol circuits. The loads and other components whose functions aresubstantially the same as those in the preceding embodiments areindicated by corresponding reference characters. Further, in thisembodiment, the control section C of the system is shown to be the sameas that in FIG. 5. However, it should be noted that the motors M,', M MM M and the heaters k h h are all rated for 200 v. and may not beprovided with intermediate terminals, unlike in the precedingembodiments.

Assuming that input terminals'R, S, T are connected with 400 v. powerlines, the voltage relay Ry operates to actuate the auxiliary relay MRand accordingly to energize the coil MC of the electromagneticcontactor. Therefore, contacts MS is closed which contacts M8, isopened, and 400 v. power is applied to the 400 v./200 v. transformer Trwhich supplies the loads with 200 v. power. On the other hand, if thevoltage of power system connected with the input terminals R, S, T is200 v., then the voltage relay Ry will not operate and the movablecontact T of the auxiliary relay MR will remain at the normally-closedposition, i.e., at the contact T Therefore, the contacts MS are closedwhile the contacts MS are kept pen. Thus, 200 v. power is supplieddirectly to the loads bypassing the transformer Tr Though the aboveembodiment has been described as a combination of a transformer having abypass means and a voltage detecting system shown in FIG. 5, it will beunderstood that combinations with other voltage detecting or selectingmeans are possible. Further, it will be obvious that the abovearrangement is applicable to 400 v. loads provided that a 200 v./400 v.step-up transformer is used for the power transformer Trg.

As described above, according to this invention, a refrigeratedcontainer can be used easily and safely at two places where availablepower is of difierent line voltages.

In the above embodiment, it has been assumed that the lower line voltageis 200 v. and the higher voltage is mostly 400 v. More generally,however, the lower voltage may be a voltage between 180 v. and 240 v.,and any higher voltage ranging from 340 v. to 480 v. can be used for therefrigerator unit of this invention.

What we claim is:

1. A refrigerator unit for use in a freight container which may becommonly connected to available power lines of at least two classes ofline voltage, said unit comprising:

at least one duaLrated electric motor constructed so as to be adaptableto either of two classes of line voltages by simply changing electricconnections of said motor,

a first means which is connectable to electrical power lines fordiscriminating between said two classes of line voltages,

a second means for changing said electric connections of said motor, andi a third means for interlocking said first means with said second meansso as to match the rated voltage of said motor with the voltage of saidelectrical lines with which said refrigerator unit maybe connected.

2. A refrigerator unit as in claim 1, wherein:

said first means comprises two power input branches,

each branch including a power plug of a particular formation which doesnot fit a receptacle prepared for the other plug and a switch isinterlocked with a switch of the other branch so as to operatecontrari-wise, and

said first means, second means and third means comprise a single gangswitch.

3. A refrigerator unit as in claim 2, wherein:

said gang switch includes an additional pair of component switch meansconnected in a control circuit of an electromagnetic contactor forselecting a terminal which insures that the rated voltage of saidcontactor matches with the line voltage,

main contacts of said contactor being provided on the power side of saidsecond means, and I said additional pair of switches being arranged insaid gang switch in such a manner that each of said pair of switches isopened before or closed after the other component switches of thecorresponding operation are opened or closed respectively.

4. A refrigerator unit as in claim 1, wherein:

said second means comprises a group of electromagnetic contactors,

said first means comprises a voltage detecting means connected with thepower lines of the unit, and

said third means comprises an appropriate number of relays forcontrolling energization of exciting coils of said electromagneticcontactors according to the result of the de tection by said firstmeans.

5. A refrigerator unit as in claim 4, wherein said voltage detectingmeans comprises: t

a transformer connected with the power lines of the unit for providingtwo classes of secondary voltages corresponding to said two classes ofline voltages,

a quick-acting relay connected with lower voltage secondary terminals ofsaid transformer for acting quickly when the refrigerator unit isconnected with a power line of a higher voltage class but which will notact when the unit is connected with a power line of a lower voltageclass, and

a slow-acting relay connected with higher voltage secondary terminals ofsaid transformer for acting slowly whenever the refrigerator unit isconnected with either power line,

said quick-acting relay and said slow-acting relay being interlocked soas to prevent the opposite relay from operating when activated.

6. A refrigerator unit as defined in claim 4, wherein said voltagedetecting means comprises a static voltage relay of a semiconductortype.

7. A refrigerator unit as in claim 1, wherein:

said electric motor comprises a three-phase motor of which each of threedelta-connected windings or star-connected windings comprises twosubstantially equal component windings and,

said second means functions to change the connections of said componentwindings in each phase between series and parallel connections so thatsaid refrigerator can be operated with either of two line voltages, oneof which is substantially twice as high as the other voltage 8. Arefrigerator unit as in claim 1, wherein:

said electric motor comprises a three-phase, motor, and

said second means functions to change the connections of phase windingsof said motor between star connection and delta connection so that saidrefrigerator can be operated with either of two line voltages, one ofwhich is substantially )1? times as high as the other voltage.

9. A refrigerator unit as in claim 7, wherein an overload detectingelement is connected in series with one of said component windings in atleast two phase windings.

10. A refrigerator unit as in claim 8, wherein an overload detectingelement is connected in series with each of at leas two phase windings.

11. A refrigerator unit used for a freight container, comprisingelectric loads whose rated voltage is equal to one of two classes ofline voltages with either of which said refrigerator unit is to beoperated, a first means as to contributes to select one of said twoclasses of line voltages, a transformer to whose secondary terminals areconnected said electric loads and which is constructed so that thesecondary voltage thereof is equal to the rated voltage of said loadsand accordingly to said one of two line voltages when a voltage equal tothe other of said two line voltages is applied to the primary windingsthereof, a second means for disconnecting said transformer from thepower circuit and making a circuit bypassing said transformer, and athird means for interlocking said first means with said second means soas to match the rated voltage of said load with the voltage of the powerline with which said refrigerator unit is connected.

12. A refrigerator unit for use in a freight container which may beconnected to either of different electrical supply lines providing atleast two classes of line voltages without any danger of mismatchingelectrical loads with available line voltages, said unit comprising:

at least one dual-rated electrical load which maybe operated at eitherof said two classes of line voltages by changing terminal connectionsthereto.

a first means for connecting said unit to available electrical powersupply lines, a second means connected between said first means and saidload for changing said terminal connections, and

interlock means for preventing the energization of said load unless saidterminal connections are proper for matching the load to the availableclass of line voltage.

13. A refrigerator unit as in claim 12 wherein:

said first means includes voltage detecting means for automaticallydetermining the class of available line voltage connected thereto, and

said second means and said interlock means comprise electricallycontrolled switch means connected to said first means and automaticallycontrolled thereby.

1. A refrigerator unit for use in a freight container which may be commonly connected to available power lines of at least two classes of line voltage, said unit comprising: at least one dual-rated electric motor constructed so as to be adaptable to either of two classes of line voltages by simply changing electric connections of said motor, a first means which is connectable to electrical power lines for discriminating between said two classes of line voltages, a second means for changing said electric connections of said motor, and a third means for interlocking said first means with said second means so as to match the rated voltage of said motor with the voltage of said electrical lines with which said refrigerator unit maybe connected.
 2. A refrigerator unit as in claim 1, wherein: said first means comprises two power input branches, each branch including a power plug of a particular formation which does not fit a receptacle prepared for the other plug and a switch is interlocked with a switch of the other branch so as to operate contrari-wise, and said first means, second means and third means comprise a single gang switch.
 3. A refrigerator unit as in claim 2, wherein: said gang switch includes an additional pair of component switch means connected in a control circuit of an electromagnetic contactor for selecting a terminal which insures that the rated voltage of said contactor matches with the line voltage, main contacts of said contactor being provided on the power side of said second means, and said additional pair of switches being arranged in said gang switch in such a manner that each of said pair of switches is opened before or closed after the otheR component switches of the corresponding operation are opened or closed respectively.
 4. A refrigerator unit as in claim 1, wherein: said second means comprises a group of electromagnetic contactors, said first means comprises a voltage detecting means connected with the power lines of the unit, and said third means comprises an appropriate number of relays for controlling energization of exciting coils of said electromagnetic contactors according to the result of the detection by said first means.
 5. A refrigerator unit as in claim 4, wherein said voltage detecting means comprises: a transformer connected with the power lines of the unit for providing two classes of secondary voltages corresponding to said two classes of line voltages, a quick-acting relay connected with lower voltage secondary terminals of said transformer for acting quickly when the refrigerator unit is connected with a power line of a higher voltage class but which will not act when the unit is connected with a power line of a lower voltage class, and a slow-acting relay connected with higher voltage secondary terminals of said transformer for acting slowly whenever the refrigerator unit is connected with either power line, said quick-acting relay and said slow-acting relay being interlocked so as to prevent the opposite relay from operating when activated.
 6. A refrigerator unit as defined in claim 4, wherein said voltage detecting means comprises a static voltage relay of a semiconductor type.
 7. A refrigerator unit as in claim 1, wherein: said electric motor comprises a three-phase motor of which each of three delta-connected windings or star-connected windings comprises two substantially equal component windings and, said second means functions to change the connections of said component windings in each phase between series and parallel connections so that said refrigerator can be operated with either of two line voltages, one of which is substantially twice as high as the other voltage.
 8. A refrigerator unit as in claim 1, wherein: said electric motor comprises a three-phase, motor, and said second means functions to change the connections of phase windings of said motor between star connection and delta connection so that said refrigerator can be operated with either of two line voltages, one of which is substantially 3 times as high as the other voltage.
 9. A refrigerator unit as in claim 7, wherein an overload detecting element is connected in series with one of said component windings in at least two phase windings.
 10. A refrigerator unit as in claim 8, wherein an overload detecting element is connected in series with each of at leas two phase windings.
 11. A refrigerator unit used for a freight container, comprising electric loads whose rated voltage is equal to one of two classes of line voltages with either of which said refrigerator unit is to be operated, a first means as to contributes to select one of said two classes of line voltages, a transformer to whose secondary terminals are connected said electric loads and which is constructed so that the secondary voltage thereof is equal to the rated voltage of said loads and accordingly to said one of two line voltages when a voltage equal to the other of said two line voltages is applied to the primary windings thereof, a second means for disconnecting said transformer from the power circuit and making a circuit bypassing said transformer, and a third means for interlocking said first means with said second means so as to match the rated voltage of said load with the voltage of the power line with which said refrigerator unit is connected.
 12. A refrigerator unit for use in a freight container which may be connected to either of different electrical supply lines providing at least two classes of line voltages without any danger of mismatching electrical loads with available line voltages, said unit comprising: at least one dual-rated electricaL load which maybe operated at either of said two classes of line voltages by changing terminal connections thereto, a first means for connecting said unit to available electrical power supply lines, a second means connected between said first means and said load for changing said terminal connections, and interlock means for preventing the energization of said load unless said terminal connections are proper for matching the load to the available class of line voltage.
 13. A refrigerator unit as in claim 12 wherein: said first means includes voltage detecting means for automatically determining the class of available line voltage connected thereto, and said second means and said interlock means comprise electrically controlled switch means connected to said first means and automatically controlled thereby. 